Researchers at IBM are testing software that would let you tote your home or office desktop around on an iPod or similar portable device so that you could run it on any PC.

The virtual computer user environment setup is called SoulPad, and consumers install it from a x86-based home or office PC. SoulPad uses a USB (universal serial bus) or FireWire connection to access the network cards for connecting to the Internet, the computer's display, the keyboard, the main processor and the memory, but not the hard disk.

After the person disconnects the system, SoulPad saves all work to the device, including browser cookies or other digital signatures that a PC keeps in its short-term memory.

The name SoulPad comes from the concept of separating a PC into a body (processor, memory, keyboard, display) and a soul (data, applications, personal settings).

Right now, the product is in the testing phase, but SoulPad contributor Ramon Caceres, a staff member at the Wearable Computing division of IBM Research, said the technology could be licensed to hardware manufacturers that could make them into dedicated devices.

"We had been looking at how people can carry their computing environments around without carrying a laptop," Caceres said. "The SoulPad is particularly good for business travelers that carry work between home and office by carrying a small device instead of a full PC. It's also great because it puts very minimal demands on the PC that you are using at the time."

The idea of booting from portable hard drives is not new, nor is the trend of letting consumers carry their entire desktop, including programs and personal preferences, with them as they travel between home and office.

"There is no question that what we are doing and what IBM is doing will converge someday," Kate Purmal, CEO of U3, said.

IBM said three technology trends have recently made SoulPad feasible: larger, faster and cheaper portable storage devices; auto-configuring operating systems that can boot on unknown hardware without a separate installation phase; and the emergence of virtual machine technology on PC-class machines.

The SoulPad software uses 6GB of space--4GB for the auto-configuration operating system and 2GB for space needed to swap and store encrypted data.

Beyond that, the size of the drive depends on how much data the user wants to carry around, Caceres said. And while using a flash memory-based hard drive is feasible, IBM stuck with hard-disk drives to fully test the capacity of SoulPad.

IBM conducted its tests on a 60GB iPod photo using Knoppix, a Linux software derivative, as an auto-configuration OS, VMware Workstation as the virtual machine monitor and an x86 PC as the encrypted virtual machine. That is where the SoulPad software partitions personal applications such as Microsoft Word or the Firefox Web browser, along with the guest operating system and personal data the user would like to carry around.

"We chose Knoppix because this flavor of Linux is good at booting on unknown PCs without asking a lot of questions," Caceres said. "In a product version, the user would be able to configure the SoulPad boot sequence so that the device knows what data and applications they want. At the moment, we do it by hand and it takes us a little longer to boot."

Shutting down the SoulPad device and walking away takes about 20 seconds. Coming back to the same PC after attaching the SoulPad to the PC takes about two minutes.

While traveling, Caceres said the user could attach the SoulPad to a lighter laptop and switch back to a more powerful laptop while not traveling. Similarly, an insurance worker could insert his or her SoulPad into a tablet PC for on-site appraisals, then into a desktop PC for other work.